Add gpu::MailboxHolder to hold state for a gpu::Mailbox

content/renderer/media/rtc_video_decoder.h

Index: content/renderer/media/rtc_video_decoder.h
diff --git a/content/renderer/media/rtc_video_decoder.h b/content/renderer/media/rtc_video_decoder.h
index 0d99a4c8c802665d7d6c8f6d306e5f54bab96609..34d7c7c7f48b42c5f5484b682f887992b261d615 100644
--- a/content/renderer/media/rtc_video_decoder.h
+++ b/content/renderer/media/rtc_video_decoder.h
@@ -28,6 +28,10 @@ namespace base {
 class MessageLoopProxy;
 };
 
+namespace gpu {
+struct MailboxHolder;
+}
+
 namespace media {
 class DecoderBuffer;
 class GpuVideoAcceleratorFactories;
@@ -156,7 +160,8 @@ class CONTENT_EXPORT RTCVideoDecoder
   void ResetInternal();
 
   // Tells VDA that a picture buffer can be recycled.
-  void ReusePictureBuffer(int64 picture_buffer_id, uint32 sync_point);
+  void ReusePictureBuffer(int64 picture_buffer_id,
+                          gpu::MailboxHolder* mailbox_holder);
 
   void DestroyTextures();
   void DestroyVDA();